Package org.apache.bcel.generic

Class InstructionHandle

  • Direct Known Subclasses:
    BranchHandle
    public class InstructionHandle
extends Object
    Instances of this class give users a handle to the instructions contained in an InstructionList. Instruction objects may be used more than once within a list, this is useful because it saves memory and may be much faster. Within an InstructionList an InstructionHandle object is wrapped around all instructions, i.e., it implements a cell in a doubly-linked list. From the outside only the next and the previous instruction (handle) are accessible. One can traverse the list via an Enumeration returned by InstructionList.elements().
    See Also:
    Instruction, BranchHandle, InstructionList

    • Field Detail

      • i_position

        @Deprecated
protected int i_position
        Deprecated.
        (since 6.0) will be made private; do not access directly, use getter/setter

    • Constructor Detail

      • InstructionHandle

        protected InstructionHandle​(Instruction i)

    • Method Detail

      • addHandle

        @Deprecated
protected void addHandle()
        Deprecated.
        Does nothing as of 6.3.1.
        Does nothing.

      • getInstruction

        public final Instruction getInstruction()

      • setInstruction

        public void setInstruction​(Instruction i)
        Replace current instruction contained in this handle. Old instruction is disposed using Instruction.dispose().

      • swapInstruction

        public Instruction swapInstruction​(Instruction i)
        Temporarily swap the current instruction, without disturbing anything. Meant to be used by a debugger, implementing breakpoints. Current instruction is returned.

        Warning: if this is used on a BranchHandle then some methods such as getPosition() will still refer to the original cached instruction, whereas other BH methods may affect the cache and the replacement instruction.

      • updatePosition

        protected int updatePosition​(int offset,
                             int max_offset)
        Called by InstructionList.setPositions when setting the position for every instruction. In the presence of variable length instructions `setPositions()' performs multiple passes over the instruction list to calculate the correct (byte) positions and offsets by calling this function.
        Parameters:
        offset - additional offset caused by preceding (variable length) instructions
        max_offset - the maximum offset that may be caused by these instructions
        Returns:
        additional offset caused by possible change of this instruction's length

      • getPosition

        public int getPosition()
        Returns:
        the position, i.e., the byte code offset of the contained instruction. This is accurate only after InstructionList.setPositions() has been called.

      • removeAllTargeters

        public void removeAllTargeters()
        Remove all targeters, if any.

      • removeTargeter

        public void removeTargeter​(InstructionTargeter t)
        Denote this handle isn't referenced anymore by t.

      • addTargeter

        public void addTargeter​(InstructionTargeter t)
        Denote this handle is being referenced by t.

      • hasTargeters

        public boolean hasTargeters()

      • getTargeters

        public InstructionTargeter[] getTargeters()
        Returns:
        null, if there are no targeters

      • toString

        public String toString​(boolean verbose)
        Returns:
        a (verbose) string representation of the contained instruction.

      • toString

        public String toString()
        Overrides:
        toString in class Object
        Returns:
        a string representation of the contained instruction.

      • addAttribute

        public void addAttribute​(Object key,
                         Object attr)
        Add an attribute to an instruction handle.
        Parameters:
        key - the key object to store/retrieve the attribute
        attr - the attribute to associate with this handle

      • removeAttribute

        public void removeAttribute​(Object key)
        Delete an attribute of an instruction handle.
        Parameters:
        key - the key object to retrieve the attribute

      • getAttribute

        public Object getAttribute​(Object key)
        Get attribute of an instruction handle.
        Parameters:
        key - the key object to store/retrieve the attribute

      • getAttributes

        public Collection<Object> getAttributes()
        Returns:
        all attributes associated with this handle

      • accept

        public void accept​(Visitor v)
        Convenience method, simply calls accept() on the contained instruction.
        Parameters:
        v - Visitor object